Rotary apparatus and method of making the same



ROTARY APPARATUS AND METHOD OF MAKING THE SAME Filed July 12, 1955 N. R. LATHAM May 1, 1962 3 Sheets-Sheet 1 on vn INVENTOR NORMAN R. LATHAM Byw a y ATTORNEYS May 1, 1962 N. R. LATHAM 3,032,260

ROTARY APPARATUS AND METHOD OF MAKING THE SAME Filed July 12, 1955 3 SheetsSheet 2 NORMAN R. LATHAM 1 fi 4 INVENTOR BYMM )AW ATTORNEYS y- 1962 N. R. LATHAM 3,032,260

ROTARY APPARATUS AND METHOD OF MAKING THE SAME Filed July 12, 1955 3 Sheets-Sheet 3 ROTATION INVENTOR NORMAN R. LATHAM I ATTORNEYS 3,032,260 ROTARY APPARATUS AND METHGD F MAKHNG THE SAME Norman R. Latham, Latham Manufacturing Co., R0. Box 165, West Palm Beach, Fla. Filed July 12, 1955, Ser. No. 521,457 11 Claims. (Cl. 23tl-122) This invention relates to compressors, turbines, fans and like rotating apparatus, and more particularly to a novel axial flow compressor and a method for making the same.

Axial flow compressors have been in use for a considerable period of time and are advantageous in that they are highly efficient, quiet in operation and provide less frontal area than the more commonly used radial flow compressors. However, due to excessively high cost of manufacture, axial fiow compressors have been utilized mainly in jet engine installations where cost is not an important factor or in largeindustrial installations where the higher cost can be written off by greater efficiency over a long period of years. Furthermore, the axial flow compressors heretofore known are not highly versatile in that if the output is reduced or increased very far beyond its designed capacity, the compressor will surge and its output and efficiency becomes relatively small.

Accordingly, it is an object of the present invention to provide an axial flow compressor which substantially overcomes the disadvantages set forth above with no appreciable sacrifice in efficiency.

A further object of the present invention is the provision of a novel method of making an axial flow compressor which substantially reduces the prohibitive costs heretofore necessary.

Another object of the present invention is the provision of a multi-stage axial flow compressor which utilizes variation in blade pitch between stages with a constant cross-sectional area air passage to achieve compression.

Still another object of the present invention is the provision of an axial flow compressor blade assembly having improved means for retaining the blades in their proper positions.

A still further object of the present invention is the provision of a novel method of constructing an axial flow compressor blade assembly which is adaptable to economical mass production techniques and which may be practiced by conventional tools in a relatively easy manner.

These and other objects of the present invention will become more apparent during the course of the following detailed description and appended claims.

The invention may best be understood with reference to the accompanying drawings wherein an illustrative embodiment is shown.

In the drawings:

FIGURE 1 is an elevational view, partly in section, of an axial flow compressor embodying the principles of the present invention;

FIGURE 2 is an end view, partly in section, of the compressor shown in FIGURE 1;

FIGURE 3 is a fragmentary top plan view showing a blade blank inserted in a blade carrying ring;

FIGURE 4 is a vertical cross-sectional view of the structure shown in FIGURE 3;

FIGURE 5 is a view similar to FIGURE 3 showing the finished blade;

"ice

FIGURE 6 is a view similar to FIGURE 4 of the blade shown in FIGURE 5; and

FIGURE 7 is a developed view showing the relative curvatures of the blades of the various stages of the compressor.

Referring now more particularly to the drawings, there is shown in FIGURE 1 an axial flow compressor, generally indicated at 10, embodying the principles of the present invention. The compressor 10 includes a pair of spaced end plates or castings 12 between which a stator assembly 16 is rigidly mounted. A rotor assembly 18 is rotatably mounted between the end plates in cooperating relation with the stator assembly 16.

As best shown in FIGURE 1, the stator assembly 16 is composed of a first series of annular members or blade carrying rings 29 and a second series of annular members or spacer rings 22 interposed between the rings of the first series in axial alignment therewith.

Each' of the rings 20 is provided with an annular groove 24 formed in each lateral surface thereof. The inner longitudinal face 26 of each ring 20, between the grooves 24, is provided with a plurality of circumferentially spaced slots 28 which extend substantially completely across the ring 29. The depth of cut of the slots is greater than the depth of cut of the grooves 24 shown in FIGURE 1.

A compressor blade 30 is provided for each slot 28 and has a first portion disposed within the slot and a second portion extending outwardly from the longitudinal face 26. The first portion of each blade 30 includes a projection 32 extending outwardly from each lateral edge of the blade and each projection has an upper surface which registers with the adjacent surface of the annular groove 24 in the ring 20.

The spacer rings 22, like the rings 20, are T-shaped in cross-section and include annular flanges 34a'dapt'ed to engage within the adjacent annular groove .24 of the rings 20. As shown in FIGURE 1, the lateral surface engagement between the flanges 34 and the grooves 24 of the various rings serves to provide a'definite fixed relationship between the rings when the same are secured together in axial alignment. The adjacent lateral surfaces of the remainder of the rings are spaced apart so.

as to receive therebetween annular sealing gaskets or rings 36.

As shown in FIGURE 1, the first and second series of rings are secured in axial alignment by means of a plurality of annularly spaced tie rods or bolts 37 which extend through the end castings and have their ends threaded to receive suitable nuts 38. It will be seen that by tightening the nuts 38, the rings will'be moved into abutting axial alignment, as shown in FIGURE 1.

The rotor assembly 18, like the stator assembly 16, includes a first series of annular members or blade carrying rings 40, each of which has an annular groove 42 formed in each lateral surface thereof. A plurality of circumferentially spaced slots 44 are formed in the longitudinal face of each ring between the lateral surfaces of rings 40 and a plurality of blades 46 are disposed in the slots 44. Blades 46 include projections 48 similar to the projections A second series of annular members or spacer rings 50 are interposed between the rings 40. Each of the rings- 50 includes anpannular flange 52 extending from each lateral surface thereof, which flanges are adapted to engage within the adjacent annular grooves of the rings 40.

with" their lateral surfaces abutting the adjacent lateral" surfaces of the grooves 42. A series of annular sealing gaskets or-rings 54 are disposed between the remaining adjacent lateral surfaces of the abutting rings. The first and second series of rings are secured together between spaced end members 56 by means of a plurality of annularly spaced tie rods or bolts 58. As shown in FIGURE 1, each end member includes an annular flange 60 adapted to engage within the adjacent annular groove 42 of the adjacent ring 40. The ends of the tie rod 58 may be threaded to receive suitable nuts 62so that when the latter are tightened, the various rings. will be held in abutting axially aligned relation between the end members 56.

Each end casting is provided with a central horizontal opening 64 within which a stub shaft 66 is suitably journaled, as by ball bearings 68. The stub shafts 66 extend within suitable apertures formed in each end member 56 and are, fixedly secured thereto by any suitable means, such as a key or the like.

Disposed between the ball bearings 68 and the adjacent end member 56 is an annular retaining member 79 which may be a separate piece as shown, or integral with the end member 56. Suitable labyrinth'seals 72 are provided be tween the outer. periphery'of the member 76 and the adjacent surface of the opening 64-. In addition, the labyrinth seals may extend between the outer annular surface of the end members 56 and the openings 64 as well. An air bleed passageway 73 may be provided in one or both end castings so as to prevent any difference in pressure which reaches the bearings from sucking the grease out of the same. The stub shaft 66 at the inlet side of the compressor extends outwardly. through the end casting 1-2 so as to receive a suitable driving member, such as pulley 74.

' Air. is introduced into the compressor through a radial inlet opening 76 extending from the outer periphery of the end plate 12' into communication with an annular passageway78 formed in the end plate so as to register with the spacing between the rotor assembly. and the stator assembly within which the blades are disposed. It Will be noted that this space is constant in cross-sectional area throughout the axial extent of the compressor, as shown in the upper portion of FIGURE 1, and allowance for the compression of the air is obtained by varying the pitch ofthe blades from the inlet to the outlet. The end plate 14 has. a similar annular passageway 80 within which the compressed air discharging from between the rotor assembly and the stator assembly. is directed. A radially extending outlet opening 82 communicates the passage 80 with the outer periphery of the. end plate 14.

As set forth above, the present invention contemplates a novel method of making the compressor 1t and more particularly the stator and rotor blade assemblies thereof. Preferably, the entire compressor with the exception of ball bearings 68 is constructed of an aluminum alloy in cluding tie, rods 37 and 58, nuts 38 and 62 and shaft 66. In this way, Weight of the compressor is reduced to a minimum, thermalexpansion will be similar, and galvanic couples between dissimilar. materials are substantially eliminated. The. stator and rotor blade assemblies are preferably machined from high strength wrought alumi num alloy tubing, and the end plates 12 and 14 are preferably cast of aluminum alloy.

Since the construction of the stator blade assembly is substantially. identical to that of the rotor blade assembly with the exception that the two are inverted with respect to each other, the method of making the rotor blade assembly should sufiice as a description of the manner in which both of the assemblies are made. It will, of course, be understood that in making the stator blade assembly, the construction is inverse, except as otherwise noted, to that which will now be described in making the rotor blade assembly.

Referring now to FIGURES 3 and 4, each ring 40 of the rotor assembly is initially formed with the annular a a h r f. la iv y h llo W th h r n this condition, the slots 44 are milled therein by a milling tool and it will be noted that the depth of cut is substan-.. tially below the depth of cut of the annular grooves. The curvature of each slot formed in a given ring is similar to the other slots formed therein, however, the curvature of the slots in difierent rings varies from the inlet side of the compressor to the outlet side thereof, as indicated in FIGURE 7. It Will be seen that the middle stage rings have slots, the curvature of which is substantially a mean curvature with respect to the curvature of the slots in the extreme inlet and discharge stage rings. Thus, in forming the slots in each ring, the curvature of all the slots of a given ring is constant and the cross-sectional configuration of each slot is relatively flat or narrow and preferably rectangular.

When the slots are all formed on the rings, the blades 46 are then inserted therein. These blades are stamped out of a sheet of high strength aluminum alloy in blank form by a die which shapes them and at the same time, gives them a curvature which is substantially similar to the mean curvature of the slots or the curvature of the slots of the middle stage ring. As shown in FIGURE 4, the blanks are oversize with respect to the ring and have a thickness substantially equal to the thickness of the slots. In inserting the blades in the middle stage ring, the curvature of the blade will coincide with the curvature of the slot so that the same may be pressed into the slot with relative ease. However, it will be noted that the blades fit quite snugly within the slots, enabling subsequent operations to -be performed without danger that they will be displaced within their slots.

After each of the blade blanks has been inserted in a slot of the ring, finishing cuts are made in. the lateral edges of the blades together with the adjacent portion of the ring as byv turning the ring with attached blades on a lathe. Stated differently, the ring with all of the blades secured in the slots thereof is cut so that the annular grooves are enlarged, as shown in FIGURES 5 and 6, and the lateral edges of the blades are flush with the lateral edge of the adjacent groove. It will be noted, however, that the increased depth of cutof the annular grooves is not as great as the depth of cut of the slots. In this manner, the first portion of each blade disposed within the slot has the upper surface of its projection flush with the upper surface of the annular groove and the lateral edges thereof flush with the lateral surface of the annular grooves.

After the finishing cuts are made as indicated above, the lateral edges of the second portion of the blades are dressed to a greater amount to give axial clearance between the rotor blades and the stator blades. In making the rotor, radial clearance is obtained after the entire rotor is assembled by dressing the outer edge or tips of the blades together; In the case of the stator assembly, this procedure is followed on each stator ring individually rather than after all of the rings have been assembled. It will be appreciated that all of these operations may be performed on a conventional lathe,

It will be noted that in forming the rotor blade rings adjacent the discharge or inletend of the compressor, the curvature of the slots will vary in pitch from theicurviature of the blade blank-s. However, since this difference is relatively slight, when the blade blanks are pressed into the slots, the blanks will assume the varying curvature. With this procedure, it is necessary only to have a single die to form all of the blade blanks and yet, the finished blades of the compressor may vary in curvature from the inlet end to the discharge end.

After each ring of the first series of rings 40 has been constructed as indicated above, the assembly is put together by interposing a spacer ring '56 between each of the rings 49. These spacer rings may be identical in shape and it will be noted that a sealing ring 54 is disposed between the lateral faces below the flanges 52 and the adjacent lateral face of the rings 49. The end plates 56 are then secured in position and the tie rods 58 inserted therethrough. Nuts 62 are then threaded on the end of the tie rods and tightened so as to secure the assembly together as a unit. It will be noted that in tightening the nuts 62, the lateral face of each annular groove 42 will abut the lateral face of the flange of the adjacent spacer ring so that the blade carrying rings 40 are positively and accurately maintained in spaced relationship with respect to each other.

The specific compressor illustrated in the drawings is particularly adapted to be used as a supercharger for gasoline engines. Thus, in order to maintain a high velocity flow to keep the gasoline in suspension, the axial extent of the blades is relatively short. For ordinary use, better eiiiciency would result with larger air passages and lower velocities. However, where longer blades are utilized as in such larger air passages, the difference in blade speed between the root of the blade and the tip of the blade becomes quite pronounced. In this case, the blades are given a twist so that the inlet angle at the root is different than the inlet angle at the tip. Where such twist is necessary, it may be formed in the blanks by the same die that stamps them out and gives them their curvature. As noted above, in inserting the blanks in the rings adjacent the inlet and outlet, the increased or decreased curvature of the slots thereof will cause the blades to assume the respective curvatures thereof and in this manner, the variance in twist is also taken care of.

Of further significance in connection with the specific compressor illustrated, is the problem of providing adequate clearance between the rotor and stator. As shown, the clearance between the tip of the stator blade and the rotor spacer has been made approximately twice the corresponding clearance between the rotor blade and the stator spacer. This clearance has been found to be desirable to eliminate the possibility of the stator blades touching. If the stator blade should touch the rotor spacer even the slightest, the heat generated would cause the rotor spacer to expand thus making the situation much worse. With a rotor blade, touching of a stator spacer would cause the latter to expand away from the touch.

Where it is desired to obtain the highest efficiency, the radial clearances must be reduced to a minimum and this requires the accurate maintenance of the parallelism of the apparatus during assembly. To insure this latter condition, the rotor spacers may be initially formed somewhat oversize in outside diameter. When the rotor is assembled, a finishing cut is taken on the spacer outside diameter as well as the tips of the blades. In the case of the stator, the blades are slightly oversize in length and the inside diameter of the spacers slightly undersize. The stator may then be assembled and with a vertical milling cutter and rotary table, the tip oversize is milled off so as to make it prefectly true. In both cases, match lines may be used on the completed assemblies so that if and when they are disassembled, they will go back exactly the same as they were machined when reassembled. This procedure, however, is necessary only where highest efficiencies are demanded.

From the above, it will be appreciated that the stator and rotor blade assemblies of the present invention may be constructed without excessive cost. For example, the blades themselves may be stamped out from a sheet of aluminum alloy or the like. This feature is extremely important in that the construction of the blades has heretofore constituted the greatest single cost in the manufacture of the compressors. The simply constructed and formed blade blanks of the present invention are mounted on the blade carrying rings by simply pressing the same into a receiving slot, and of particular importance, is the fact that the curvature of the blade blanks may thus be changed to assume the curvature of the slot. Here again, the same blade blanks may be used throughout the entire assembly even though the curvatures of the finished blades vary throughout. Furthermore, the blades of each stage of the compressor may all be finished by a single operation. For example, the rough cut ring with the blades inserted in the slots thereof, may be mounted on a lathe and the leading edge of all of the blades may be cut during the turning of the lathe as well as the adjacent portion of the ring itself. Likewise, the finishing of the leading and trailing edges of the blades, since they are perpendicular to the axis of the rings, may be formed in a single operation. In the case of the rotor, the tips of the blades may all be sized and finished in a single operation. Since the air fiow space between the stator and rotor is constant in area throughout the axial extent of the compressor, the rings of each assembly may be formed from the same stock thus making it simply a matter of choice as to the number of stages desired with no appreciable modification required to vary the number of stages. In general, the method of constructing the rotor and stator blade assemblies of the present invention obviates the necessity of making each blade and/or stage separate as was heretofore necessary in the construction of axial flow compressors.

In conjunction with the economical method of making the individual compressor rings, attention is directed to the novel manner in which the blades are retained in position when the various rings are assembled. As mentioned above, since the first portion of the blades within the slots is cut in the same operation as the finished annular grooves in the rings, the adjacent surfaces of the blades register with the surfaces of the annular grooves. Thus, when the spacer rings are positioned adjacent the blade carry ing rings, the flanges of the spacer rings engage the surfaces of the annular grooves of the blade carrying rings and hence, the upper surface of the projections on the blades. When the tie rods are tightened in position, the engagement of the flange of the spacer rings with the upper surface of the projections securely maintains the blades within their slots. It will be appreciated that this method of retaining the blades in the rings constitutes a simplification of the complicated and costly dovetail arrangements heretofore utilized.

The provision of an inexpensive compressor constructed in accordance with the present invention makes possible the use of axial flow compressors for many jobs heretofore considered impractical. For example, the present compressor may be used to good advantage as a super charger for an internal combustion engine. It has been found that the compressor of the present invention is highly eflicient in such use and results in a greater savings of gasoline. Heretofore, all superchargers with the exception of aircraft superchargers have been so inefficient that the} result in a greater consumption of fuel at even throttle operation. The compressor of the present invention may be constructed small enough in diameter to mount in any engine compartment and is extremely quiet in operation. It has also been found that during intermittent peak operation, the present compressor will raise the horsepower of the engine without the use of special fuels and in no way will shorten the life of the engine.

In operation, the compressor is driven from a suitable source by means of a belt or chain drive suitably connected to the pulley 74. Air entering the inlet opening 76 will pass into the annular passageway 78 and thence, into the flow space between the rotor assembly and stator assembly in which the blades are disposed. In the axial flow compressors heretofore utilized, the blade pitch of the ditferent stages of the rotor remained the same and the annular area between the rotor and stator was varied. With the present invention, this annular area remains constant and the pitch of the blades varies from stage to stage.

In the specific compressor as shown in FIGURE 1, by maintaining a high axial air velocity the necessity of changing the blade angle from the root to the tip is eliminated, thereby reducing the pitch angle of the leading edge of the rotor blade to 20 or less. Reductions or in- '2' creases in air quantity change the air angle very little, thereby reducing the possibility of surging.

The design of the leading edge of the rotor blades is also an important feature of the present invention. For example, when operating at design capacity, the relative direction of the air on any given blade may be along the arrow A, as shown in FIGURE 5, which lines up with the body of the blade. When the discharge is considerably restricted, the relative direction of the air is along the arrow B, and since this flow is a much smaller quantity of air, the actual leading point of the blade is more important in this case than the direction of the body of the blade. Thus, there is relatively no surging at any capacity with the compressor of the present invention.

It will be understood that while the manner of constructing the present compressor, as well as the manner in which the blades are retained in position, is illustrated in connection with an axial flow compressor having a constant area of air flow space throughout, these features are equally as applicable to a compressor having a variable area air flow space. Furthermore, the invention is not restricted in its application to axial flow compressors. The procedures and constructions set forth may be readily applied to other machines, such as turbines and axial fiow fans. It applies to impulse turbines and particularly reaction turbines since the latter are similar to axial flow compressors except in reverse.

It is also to be understood that the form of the invention herewith shown and described is to be taken as the preferred embodiment of the same and that various changes may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. An apparatus of the type described comprising a pair of spaced end plates, a stator assembly fixed between said end plates, and a rotor assembly rotatable between said end plates in cooperating relation with said stator assembly, said stator assembly comprising a plurality of axially aligned rings presenting an inner cylindrical surface, said cylindrical surface having a series of axially spaced circumferentially arranged groups of relatively thin Stator slots formed therein, the pitch of the stator slots of each group varying from one end plate to the other, and a relatively thin stator blade in each stator slot corresponding in pitch thereto, said rotor assembly comprising a plurality of axially aligned rings presenting an outer cylindrical surface parallel with the inner cylindrical surface of said stator assembly, said outer cylindrical surface having a series of axially spaced circumferentially arranged groups of relatively thin rotor slots formed therein, the pitch of the rotor slots of each group varying from one end plate to the other, and a relatively thin rotor blade in each rotor slot corresponding in pitch thereto.

2. Apparatus as defined in claim 1 wherein the rings of said stator assembly and said rotor assembly include blade carrying rings within which the respective stator and rotor slots are formed and spacer rings interposed between said blade carrying rings, each of said blade carrying rings having annular grooves formed in the lateral surfaces thereof adjacent the respective inner and outer cylindrical surfaces thereof, said spacer rings having annular flanges on the lateral surfaces thereof adjacent the respective inner and outer cylindrical surfaces thereof arranged to engage within respective annular grooves formed in said blade carrying rings. 7

3. Apparatus as defined in claim 2 wherein said stator blades and Said rotor blades include projections extending outwardly therefrom, said projections being disposed within the slots of respective blade carrying rings adjacent the annular grooves therein for engagement with the annular flanges of said spacer rings.

4. Apparatus as defined in claim 3 wherein said annular grooves and said annular flanges include adjacent abutting lateral. surfaces, and wherein the remaining adjacent lateral surfaces of said blade carrying rings and said spacer rings are spaced apart to receive therebetween annular sealing gaskets.

5. Apparatus as defined in claim 1 wherein the rings of said stator assembly and the rings of said rotor assembly are respectively held together by annularly spaced tie rods.

6. In an apparatus of the type described, the combination comprising a plurality of annular members, means for rigidly securing said members together in axial alignment, said members together defining a longitudinally extending continuous surface of revolution, at least one of said annular members having a longitudinal face de fining a portion of said surface of revolution and opposed lateral annular faces, the longitudinal face of said one annular member having a series of circumferentially spaced slots extending inwardly therefrom with the ends thereof communicating respectively with said lateral faces, said slots being of substantially uniform thickness throughout, a series of circumferentially spaced blades having first portions disposed in and filling said slots and second portions extending away from the longitudinal face of said one annular member, the ends of the first portions of said blades being aligned with and forming continuations of the lateral annular faces of said one member in communication with the ends of said slots, said ends adjacent each lateral face of said one member including portions facing longitudinally away from the associated lateral face and transversely away from the slots, the annular members adjacent both lateral faces of said one annular member including means defining surfaces facing in opposed directions to the longitudinally and transversely facing portions of both of said first blade portion ends and contacting the latter so that the securement of said one member in alignment with said adjacent members and the contact of the opposed surface defining means of the latter with the longitudinally and transversely facing portions of both of said first blade portion ends serve as the sole means for positively retaining said blades in said slots against movement in either longitudinal direction and in a direction away from said slots.

7. The combination as defined in claim 6 wherein said anular members include peripheral rings having T-shaped cross-sectional configurations, the T-shaped cross-sectional configuration of said one annular member being inverted with respect to the T-shaped cross sectional configurations of the adjacent annular members so as to interfit therewith.

8. In an apparatus of the type described, the combination comprising an annular member having one longitudinal face thereof provided with a plurality of circumferentially spaced slots, a plurality of blades for said slots, each of said blades including a first portion disposed in a slot and a second portion extending away from said longitudinal face, the second portion of said blades being of relatively thin elongated arcuate configuration in cross-section, the leading edge of the second portion of said blades forming surfaces greater in width than the thickness of the second portion of said blades, said leading edges being disposed in a common surface of revolution, and means for retaining the first portion of said blades in said slots.

9. The combination as defined in claim 8 wherein the first and second positions of said blades are of the same thickness.

10. The combination as defined in claim 8 wherein said blades are formed from stock of uniform thickness.

11. The combination as definedin claim 8 wherein the trailing end of the second portion of said blades form surfaces greater in Width than the thickness of the second portion of said blades and disposed in a common surface of revolution.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Buck Feb. 25, 1908 Tedman Nov. 5, 1929 Price Mar. 21, 1950 Smith Aug. 29, 1950 Sollinger et a1. Nov. 13, 1951 Howard Sept. 16, 1952 10 Krouse et a1. May 5, 1953 Feilden Oct. 6, 1953 Boyd et a1 Sept. 14, 1954 King et a1 May 15, 1956 FOREIGN PATENTS Great Britain Oct. 26, 1945 Great Britain Mar. 24, 1947 Great Britain Mar. 24, 1947 

